The Dwindling Y Chromosome

Why is it shrinking at such an alarming rate? And does it spell the end of men?

There has been a fear that in the distant future, the male sex will become extinct, leaving women to come up with a new method of reproduction. The fear arises from the fact that the Y chromosome has been shrinking at an alarming rate. The pairing of the two human chromosomes, X and Y, determines the sex of an offspring. A baby with XY chromosomes is male, and XX female. The Y chromosome was once the same size as the X chromosome, both of them carrying some 800 genes. But today, the Y chromosome carries only 27 such genes, leading many to theorise that the Y chromosome will continue to shrink and eventually disappear completely.

A new study has, however, found that these fears are unfounded. It argues that the Y chromosome is unlikely to disappear. According to this study, the Y chromosome will maintain its current size and remaining genes and thus survive.

For the study, conducted by researchers from University of California and published in PLOS Genetics, the Y chromosomes of eight African and eight European men were examined. The researchers found that not only had the Y chromosomes’ rate of loss dramatically reduced, the Y chromosome among the people being studied were nearly identical. This similarity is strange, given the geographical distance between them.

The researchers claim that the reason for this similarity is natural selection; the Y chromosome has been shedding genes and selectively purging itself of harmful mutations. In the case of the X chromosome, the reason that it does not need to shed its genes and purify itself is its inherent nature. In females, in the event of harmful mutations, the X chromosome has a partner with which it can swap DNA and repair itself. Males do not have that luxury since they possess XY chromosomes. And according to the researchers, since this combination cannot fix itself in case of genetic mutations, they simply shed faulty genes.

The lead researcher of the study, Melissa Wilson Sayres, told the Guardian, “Natural selection is acting on the Y chromosome and has maintained the genes pretty well… All the evidence points toward it not disappearing.” That’s a relief!

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